This invention relates to polymeric materials having improved weathering resistance. Particularly, although not exclusively, the invention relates to polymeric materials which include a halogen-containing polymer and, especially, to polymeric materials which include both a halogen-containing polymer and an acrylic polymer.
Halogen-containing polymers, for example, polyvinyl chloride (PVC) are relatively cheap and readily available materials. They have been used outdoors in buildings and glazing. However, the weatherability, for example the light stability of halogen-containing polymers is poor, leading to relatively short lifetimes particularly in pigmented formulations.
Acrylic materials are used in a variety of applications, for example buildings, including glazing, automotive lights, instrument dials, light diffusers, lenses, medical diagnostic devices, signs, bath/sanitary ware, because of their toughness, weatherability, appearance and stability characteristics. They may be used as capstock material to provide a coating layer over a substrate thermoplastic material and hence impart the advantageous properties of acrylic compounds to the underlying thermoplastic material. One example of the use of acrylic materials as capstocks is described in U.S. Pat. No. 5,318,737 in which suitable acrylic compositions for coextrusion with acrylonitrile-butadiene-styrene (ABS) are described for a variety of end-uses.
In many application areas the retention of beneficial properties following exposure to sunlight etc is important. Acrylic materials themselves generally have exceptional weathering performance and when formulated correctly can be used to impart these properties to underlying plastics materials. Blends of PVC and acrylic materials may be attractive in some situations. For example, compared to unmodified acrylics, acrylics modified by addition of PVC may be cheaper, have increased toughness, exhibit reduced flammability and have desireable melt-flow properties. However, whilst the weathering performance of an acrylic/PVC blend is generally improved compared to the PVC alone, the addition of PVC to acrylics reduces the weathering performance compared to unmodified acrylics. Thus, an acrylics/PVC blend may exhibit unacceptable colour stability, degradation in appearance and mechanical properties following exposure to sunlight or in weathering tests. In fact, unmodified pigmented acrylic/PVC blends behave similarly to PVC itself in that they begin to lighten (xe2x80x9cchalkxe2x80x9d) after several thousands hours accelerated weathering exposure in both xeno and QUV A machines. The xe2x80x9cchalkingxe2x80x9d phenomenon is well known to those skilled in the art of PVC material formulation and generally manifests itself as a lightening in material colour, which is measured as a positive xe2x80x9cxcex94Lxe2x80x9d in weathering testing. For unmodified pigmented acrylic/PVC blends the time that this xe2x80x9cchalkingxe2x80x9d occurs is dependent upon the amount of PVC present in the blend, but even at concentrations of  less than 20% w/w PVC a noticeable colour shift (xcex94E) occurs after 6000 hours exposure.
It is an object of the present invention to address the above-described problems.
According to a first aspect of the invention, there is provided a polymeric material comprising a halogen-containing polymer which contains between 5 to 70% by wt of halogen and 0.1 to 25% by wt of an inorganic hydroxide of zinc, magnesium, molybdenum, antimony, aluminium, tin, copper, manganese, cobalt or iron.
According to a second aspect, there is provided a method of manufacturing a polymeric material which comprises a halogen-containing polymer which contains between 5 to 70% by wt of halogen and 0.1 to 25% by wt of an inorganic hydroxide of zinc, magnesium, molybdenum, antimony, aluminium, tin, copper, manganese, cobalt or iron, the method comprising melt blending, preferably by extrusion, preferably between 150xc2x0 C. to 250xc2x0 C., said halogen-containing polymer and said inorganic hydroxide.
According to a third aspect, there is provided the use of an inorganic hydroxide of zinc, magnesium, molybdenum, antimony, aluminium, tin copper, manganese, cobalt or iron in a polymeric material comprising a halogen-containing polymer which contains between 5 to 70% by wt of halogen for improving the weathering resistance of said halogen-containing polymer, especially their colour stability.
The halogen-containing polymer is preferably a chlorine-containing polymer. The only halogen in said polymer is preferably chlorine. Said polymer may be a polyvinylchloride, polyvinyldichloride, polyvinylidene chloride, chlorinated PVC or chlorinated polyolefin. Said polymer is preferably chosen from a polymer or copolymer of vinyl chloride or vinylidene chloride. A particularly preferred halogen-containing polymer is polyvinyl chloride (PVC). The halogen containing polymer may contain other materials, as known to those skilled in the art, for example pigments, fillers, impact modifiers, lubricants, UV stabilisers, thermal stabilisers and viscosity modifiers. Said halogen containing polymer suitably includes at least 75% by wt of polymer, preferably at least 80% by wt, more preferably at least 90% by wt, especially at least 95% by wt of polymer. Said halogen containing polymer may consist essentially of polymer, especially PVC.
Suitably, the halogen containing polymer, preferably in the absence of any fillers or other ingredients (e.g. thermal stabilisers or viscosity modifiers), includes at least 10% by wt, preferably at least 20% by wt, more preferably at least 30% by wt, especially at least 40% by wt and most preferably at least 45% by wt of halogen, especially chlorine. The halogen containing polymer, preferably in the absence of said aforementioned ingredients, preferably includes less than 70% by wt, preferably less than 60% by wt, especially less than 57% by wt halogen, especially chlorine. Preferably, said halogen containing polymer includes no halogen other than chlorine.
Said polymeric material may include at least 0.5% by wt, suitably at least 0.75% by wt, preferably at least 1% by wt, especially at least 2% by wt, of said inorganic hydroxide. Said polymeric material may include 20% by wt or less, suitably 15% by wt or less, preferably 10% by wt or less of said inorganic hydroxide.
Said inorganic hydroxide may be selected from aluminium hydroxide, zinc hydroxide, iron hydroxide, magnesium hydroxide and tin hydroxide. Said inorganic hydroxide could be antimony hydroxide. Preferably said inorganic hydroxide is selected from magnesium hydroxide, antimony hydroxide, zinc hydroxide and aluminium hydroxide and, of the aforesaid, magnesium hydroxide, antimony hydroxide and zinc hydroxide are preferred. Preferably, said inorganic hydroxide comprises magnesium hydroxide. Preferably, said inorganic hydroxide does not include a material which comprises or consists of aluminium hydroxide. Said inorganic hydroxide may include more than one inorganic hydroxide. However, said inorganic hydroxide preferably consists essentially of magnesium hydroxide.
The weight average particle diameter of particles of said inorganic composition is suitably less than 250 xcexcm, preferably less than 100 xcexcm, more preferably less than 50 xcexcm, especially less than 10 xcexcm, suitably so that the material can have a high surface gloss. In some cases, the diameter may be smaller, for example less than 0.1 xcexcm or below. In this case, the particles may be sufficiently small so that they do not scatter light when incorporated into the acrylic material and, accordingly, clear acrylic materials may be made.
Said polymeric material may include an acrylic polymer. Said acrylic polymer may comprise a homopolymer or a copolymer (which term includes polymers that have more than two different repeat units) of an alkyl(alk)acrylate or a copolymer comprising acrylonitrile, especially a copolymer which includes styrene and acrylonitrile, optionally in combination with other material (especially polymeric material).
Where said acrylic polymer is an alkyl(alk)acrylate, it is preferably a homo or copolymer of at least one C1-C6 alkyl (C0-C10alk)acrylate and is more preferably a copolymer made by polymerising a monomer mixture comprising 50-99% wt of an alkyl methacrylate and 1-50% wt of an alkyl acrylate. The alkyl methacrylate is preferably a C1-C4 alkyl methacrylate, for example methyl methacrylate. The alkyl acrylate is preferably a C1-C4 alkyl acrylate, for example methyl, ethyl or butyl acrylate. The molecular weight (MW) of the alkyl(alk)acrylate is preferably at least 20,000 and, more preferably, is at least 50,000. The molecular weight may be 500,000 or less, preferably 200,000 or less, more preferably 150,000 or less.
Where said acrylic polymer is a copolymer comprising acrylonitrile, it may be an acrylic-styrene-acrylonitrile (ASA) polymer, acrylonitrile-EPDM-styrene polymer (AES), styrene-acrylonitrile (SAN) polymer, olefin-styrene-acrylonitrile (OSA) polymer or acrylonitrile-butadiene-styrene (ABS) polymer, with ASA, AES and SAN being preferred.
Suitable copolymers comprising acrylonitrile include at least 15% by wt, more preferably at least 20% by wt, more preferably at least 25% by wt, especially at least 30% by wt of acrylonitrile; and less than 50% by wt, preferably less than 40% by wt, more preferably less than 35% by wt of acrylonitrile.
Suitable copolymers of acrylonitrile include at least 40% by wt, preferably at least 50% by wt, more preferably at least 55% by wt, especially at least 60% by wt styrene; and less than 80% by wt, preferably less than 70% by wt, more preferably less than 65% by wt, of styrene.
Where said polymer comprising acrylonitrile comprises a copolymer comprising acrylonitrile and styrene together with another material, said material may be selected from an olefin, acrylic or EPDM. The amount of the latter mentioned components may be in the range 0 to 20% by wt, preferably 0 to 15% by wt, especially 0 to 10% by wt.
The polymeric material (especially one comprising an acrylic polymer comprising an alkyl(alk)acrylate) may additionally comprise between 0-60 wt %, preferably 20-60 wt % of a rubbery copolymer. By a rubbery copolymer, we mean materials which have a glass transition temperature which is less than room temperature, preferably less than 0xc2x0 C., e.g. less than xe2x88x9220xc2x0 C. We also include block copolymers which include a rubbery, low Tg block, often with harder, higher Tg blocks. Such materials are well known for use as toughening agents for improving the impact resistance of acrylic materials. Suitable rubbery copolymers include copolymers of acrylates, methylacrylates, styrene, acrylonitrile and/or olefins (especially butadiene). Examples of suitable materials include styrenexe2x80x94butadiene rubbers, styrene-olefin copolymers, methacrylate-butadiene-styrene (MBS) terpolymers, styrene-acrylonitrile copolymers and core-shell type particles based on methyl methylacrylate and alkyl acrylate copolymers, e.g. butyl acrylate and styrene. Preferred types of rubbery copolymer are core-shell particles such as are well-known in the art and described in e.g. U.S. Pat. No. 5,318,737.
Said polymeric material preferably includes 0.1 to 99.8% by wt of said halogen-containing polymer. Said polymeric material may include at least 2% by wt, suitably at least 5% by wt, preferably at least 10% by wt, more preferably at least 25% by wt, especially at least 30% by wt of said halogen-containing polymer. Said polymeric material may include 80% by wt or less, suitably 70% by wt or less, preferably 60% by wt or less, especially 50% by wt or less of said halogen-containing polymer.
Said polymeric material preferably includes 0.1 to 99.8% by wt of said acrylic polymer. Said polymeric material may include at least 5% by wt, suitably at least 10% by wt, preferably at least 24.9% by wt, more preferably at least 40% by wt, especially at least 60% by wt of said acrylic polymer. Said polymeric material may include 94.9% by wt or less, suitably 90% by wt or less, preferably 80% by wt or less, more preferably 70% by wt or less of said acrylic polymer.
The ratio of the weight of halogen-containing polymer to acrylic polymer in said polymeric material may be at least 0.3, especially at least 0.4. The ratio may be less than 2, preferably less than 1.5, especially less than 1.1. Where the acrylic polymer is ASA and the halogen-containing polymer is PVC, the ratio may be about 1. Where the polymer is an alkyl(alk)acrylate and the halogen-containing polymer is PVC, the ratio may be in the range 0.35 to 0.6, especially 0.4 to 0.5.
Preferably, the halogen containing polymer is compatible with the acrylic polymer in such a way that it can be melt blended to form the polymeric material without undue difficulty.
Other additives such as UV stabilisers, colorants, lubricants etc. that are commonly found in acrylic materials may be present in the polymeric material. The polymeric material may additionally contain one or more inorganic materials selected from oxides, carbonates, borates, stearates, chlorides or bromides of zinc, magnesium, molybdenum, antimony, aluminium, tin, copper, manganese, cobalt or iron. The polymeric material may include between 0.5 and 15% by wt of at least one of the aforesaid inorganic materials, preferably 0.5 -5%.
Said polymeric material suitably includes less than 1 wt %, preferably less than 0.5 wt %, more preferably less than 0.1 wt %, especially substantially no hydrotalcite. Said polymeric material suitably includes less than 1 wt %, preferably less than 0.5 wt %, more preferably less than 0.1 wt %, especially substantially no basic calcium-aluminium-hydroxy carboxylates. Said polymeric material suitably includes less than 1 wt %, preferably less than 0.5 wt %, more preferably less than 0.1 wt %, especially substantially no polyols and/or hydroxyl group-containing isocyanurate.
In a preferred embodiment, the acrylic polymer is melt blended with the inorganic hydroxide at a temperature between 150 to 230xc2x0 C., more preferably 180 to 220xc2x0 C. prior to melt blending with the halogen containing polymer. More preferably all of the ingredients are melt blended together between 150 to 230xc2x0 C., more preferably 160 to 200xc2x0 C. and particularly 170 to 195xc2x0 C.
The polymeric material may be made in the form of sheets, film, powders or granules. It may be extruded or moulded into various shapes or coextruded or laminated onto other materials, for example rigid or foamed forms of ABS, PVC, polystyrene polymers including HIPS and other modified styrene polymers, or polyolefins. The material may also be coextruded or laminated onto metals. Material as described in the form of sheets (e.g. coextruded or laminated sheets) may be thermoformed or otherwise formed into a desired shape by a suitable means.
The invention extends to a polymeric material comprising:
a) 0.1 -99.8% by wt of an acrylic polymer;
b) 0.1 -99.8% by wt of a halogen containing polymer which contains between 5 to 70% by wt of halogen;
c) 0.1 to 25% by wt of an inorganic hydroxide of zinc, magnesium, molybdenum, antimony, aluminium, tin, copper, manganese, cobalt or iron.
The invention extends to a method of manufacturing a polymeric material which comprises:
a) 0.1 -99.8% by wt of an acrylic polymer;
b) 0.1 -99.8% by wt of a halogen containing polymer which contains between 5 to 70% by wt of halogen;
c) 0.1 to 25% by wt of an inorganic hydroxide of zinc, magnesium, molybdenum, antimony, aluminium, tin, copper, manganese, cobalt or iron;
which process comprises melt blending, by extrusion, between 150 to 250xc2x0 C., said acrylic polymer, said halogen containing polymer and said inorganic hydroxide.
The invention extends to the use of an inorganic hydroxide of zinc, magnesium, molybdenum, antimony, aluminium, tin, copper, manganese, cobalt or iron, in a polymeric material which includes a halogen-containing polymer, for improving the weathering resistance of the halogen-containing polymer.
A polymeric material as described herein may be supplied in the form of pellets. The pellets may then be thermally processed for any downstream application. Alternatively where a polymeric material includes an acrylic polymer, a solid form (e.g. pellets) comprising said acrylic polymer and said inorganic hydroxide may be supplied for subsequent mixing with a said halogen-containing polymer Thus, the invention extends to a solid form comprising said acrylic polymer and said inorganic hydroxide, wherein the xe2x80x9c% by wtxe2x80x9d expressed herein for said acrylic polymer and said inorganic hydroxide represent xe2x80x9cparts by weightxe2x80x9d in said solid form.
The invention extends to a weather-resistant component comprising an acrylic material according to said first aspect or manufactured in a method according to the second aspect.
Said component may be a coextruded or laminated component which includes said acrylic material.
Said component may be for use in construction.
Said component may be for use in construction of a building. For example, it could be a solid or coextruded building component, for example a soffit board, barge board, fascia board, cladding board, siding, gutter, pipe, shutters, window casement, window board, window profile, conservatory profile, door panels, door casement, roofing panel, architectural accessory or the like.
Said component may be for use in constructing a vehicle or in another automotive application, both as a bulk material or as a coextruded laminate. Such applications include, but are not limited to, decorative exterior trim, cab moldings, bumpers (fenders), louvers, rear panels, accessories for buses, trucks, vans, campers, farm vehicles and mass transit vehicles, side and quarter panel trim or the like.
Said component may be used in applications both indoors or outdoors, for example bathtubs, spas, shower stalls, counters, bathroom fixtures, toilet seats, kitchen housewares, sinks, refrigerator liners or bodies, fencing, trash cans, garden furniture or the like.
The invention further extends to a weather-resistant component for an outdoor application comprising a polymeric material according to said first aspect or manufactured in a method according to the second aspect
Outdoor applications include the aforementioned building components and include signage, for example for petrol stations (or the like).
The invention further extends to a weather-resistant extrusion comprising a polymeric material according to said first aspect or manufactured in a method according to the second aspect.
The invention extends to the use of a component made of a polymeric material according to the first aspect or manufactured in a method according to the second aspect in construction and/or in outdoor applications.
The invention extends to a building comprising a component made out of an acrylic material according to the first aspect or manufactured in a method according to the second aspect.
The invention extends to a component which includes a substrate and a capstock material wherein at least one of either the substrate or the capstock material is an acrylic material according to the first aspect or manufactured in a method according to the second aspect.
Any feature of any aspect of any invention or embodiment described herein may be combined with any feature of any aspect of any other invention or embodiment described herein.
The invention will be further described with reference to the following Examples.